Micromirrors are presently used in a continuously increasing number of applications. These applications include, for example, projectors, scanners, or the like. The advantage of the micromirrors is that they occupy little space and may therefore be used very flexibly.
Micromirrors are typically micro-electromechanical elements which are structured and manufactured, for example, with the aid of the conventional methods from semiconductor processing.
Different methods may be used to implement the deflection of the mirrors in such a micromirror. For example, electrostatic drive methods, magnetic drive methods, piezoelectric drive methods, or the like may be used. Some drive methods only offer the option of tilting the mirror in one direction. Other drive methods also offer the option of tilting the mirror in two directions. The mirror thus carries out a rotational movement about the tilt axis or tilt axes.
Due to the relatively large rotational mass of the drive of such a micromirror, the overall structure, or parts thereof, made up of a quasistatic mirror, a resonant mirror, mechanical fixing elements, magnets, electronic parts, including connecting surfaces, in particular adhesive surfaces, may be excited into undesirable oscillations.
Connecting parts made of plastic, in particular adhesive bonds, may have a significant plastic deformation in the event of such oscillations, which becomes noticeable in an undesirable energy dissipation. Mass movements in the z direction, i.e., perpendicular to the chip surface or mirror surface, are particularly critical with respect to the energy decoupling.
Such a mass movement in the z direction is part of the normal operation of such a micromirror, however, because of the basic drive arrangement in conventional micromirrors. FIG. 9 shows the schematic structure of such a micromirror, which is described, for example, in German Patent Application No. DE 10 2012 206 291.
The micromirror of FIG. 9 has a drive spring F1, via which a drive body A is connected to holder H. Mirror SP is coupled to drive body A via a second spring F2. Furthermore, a coil S, which is permeated by a magnetic field generated by magnet M, is situated on the edge of drive body A. Depending on the orientation of the magnetic field, the drive body is moved upward or downward, i.e., in the z direction, at the edge which has the coil. If the drive body is set cyclically into such a rotational movement, the mirror is also set into a rotational movement. As is apparent in FIG. 9, the movement of drive body A in the z direction is an elementary part of the drive of FIG. 9 and cannot be avoided in the drive shown.